Chirp Managed Laser (CML) transmitter

Abstract

A fiber optic communication system comprising: an optical signal source adapted to receive a binary base signal having a bit period T, and generate a first signal, wherein the first signal is frequency modulated; and an optical spectrum reshaper (OSR) adapted to reshape the first signal into a second signal, wherein the second signal is amplitude modulated and frequency modulated; characterized in that: the frequency excursion of the first signal is adjusted such that the frequency excursion is substantially equal to the ratio of the bit period of the digital base signal to total dispersion of the transmission fiber, whereby to increase the tolerance of the second signal to dispersion in a transmission fiber.

1. A method for transmitting a binary base signal through an optical fiber, comprising:
 modulating a laser with a binary base signal having a bit period T, and generating a first signal from the laser, wherein the first signal is frequency modulated having a frequency excursion, Δυ; 
 reshaping the first signal into a second signal, wherein the second signal is amplitude modulated and frequency modulated; and 
 directing the second signal into the optical fiber having a transmission fiber length, L, in km and a dispersion, D, in ps 2 /km; 
 characterized in that: 
 the frequency excursion of the first signal, Δυ, in GHz is substantially equal to the ratio of the bit period of the digital base signal, T, in picoseconds, to the product of the transmission fiber length, L, and the dispersion of the transmission fibers, D, whereby to reduce the bit error rate at transmission distance, L. 
 
   
   
     2. A method according to  claim 1  wherein the laser is a distributed feedback (DFB) laser. 
   
   
     3. A method according to  claim 1  wherein reshaping the first signal into a second signal comprises passing the first signal through a filter. 
   
   
     4. A method for operating a transmitter including a laser having an output thereof coupled to an optical fiber having a length L and a dispersion D, the method comprising:
 modulating a laser with a binary base signal having a bit period T such that the laser outputs a frequency modulated light having a frequency excursion Δυ; and 
 coupling the output of the laser to the optical fiber; 
 wherein the frequency excursion Δυ is substantially equal to the ratio of the bit period of the digital base signal T to the product of the transmission fiber length L and the dispersion D of the transmission fiber, whereby to reduce the bit error rate at a transmission distance of length L. 
 
   
   
     5. The method of  claim 4 , further comprising a filter positioned between the laser and the optical fiber. 
   
   
     6. The method of  claim 4 , wherein the laser is a distributed feedback (DFB) laser. 
   
   
     7. A method for transmitting binary data comprising:
 modulating a laser with a binary base signal having a bit period T such that the laser outputs a first frequency modulated signal having a frequency excursion Δυ; 
 transmitting the first frequency modulated signal through a filter such that the filter outputs a second frequency modulated signal having increased amplitude modulation relative to the first frequency modulated signal; and 
 coupling the second frequency modulated signal to an optical fiber having a transmission length L and a dispersion D; 
 wherein the frequency excursion Δυ is substantially equal to the ratio of the bit period T to the product of the transmission fiber length L and the dispersion D.